1. Field of the Invention
The present invention relates, in general, to a Passive Optical Network (PON) system and method for detecting a fault in an Optical Network Terminal (ONT) and, more particularly, to a PON system and method for detecting a fault in an ONT, which can detect a faulty ONT that continuously outputs signals, or which can determine whether a faulty ONT is present by applying a trigger signal and detecting a Loss Of Signal (LOS) signal corresponding to the trigger signal when a virtual ONT is formed in a plurality of ONTs connected to an Optical Line Terminal (OLT) and then an optical signal in the section of the virtual ONT is detected.
2. Description of the Related Art
Recently, as the number of Internet users who use wireless communication rapidly increases, high-speed Internet technologies have been developed so as to provide faster Internet services to users.
A representative technology for typical high-speed Internet services is wireless Local Area Network (LAN) technology.
Optical communication systems are systems for transmitting and receiving data based on optical signals. A station-side optical line terminal is a device for relaying the transmission of data between a server that provides various types of data services to subscribers over a telephone network or the Internet, and optical network terminals that are connected to respective subscriber terminals. The optical line terminal forms optical signals required to transmit the transmission data of the server to a target optical network terminal and receive data transmitted from the target optical network terminal.
Typically, a Passive Optical Network (PON) is one of optical subscriber construction schemes for providing an optical fiber-based high-speed service to businesses or normal homes, and is configured such that Optical Network Terminals (ONTs) disposed downstream of the PON can be connected to the PON by using a splitter in an optical cable. In this case, a Time Division Multiplexing (TDM)-PON using a TDM scheme allocates or distributes downstream optical signals to subscribers and combines upstream optical signals received from subscribers.
In such a TDM-PON, the transmission and reception of data between an OLT and ONTs are conducted in such a way that, in the case of a downstream procedure, when the OLT inserts the identifier of a registered ONT into the preamble of a frame and transmits the frame, a relevant ONT sends only a frame having its own identifier to a user interface. In contrast, in the case of an upstream procedure, when the OLT dynamically allocates upstream time slots to all ONTs, the ONTs transmit data to the OLT in respective time slots allocated thereto.
In this case, the ONTs must perform the upstream procedure only in the allocated time slots. However, when a fault occurs in any one of ONTs and then the faulty ONT continuously transmits signals, a problem with the overall communication may occur.